Physically Based Rendering
Microfacet surface model
Consider any surface as a pack of facets like in diamond. In rougher surfaces, these facets are more chaotically aligned than in smoother surfaces. PBR uses this theory to imitate surface property statistically, by defining a factor "roughness".
Halfway vector:
The more these hlafway vectors are aligned to the incoming light, the more stronger will be the reflections.
Energy Conservation
When a light ray hits a surface, it splits into 2 parts: Reflection and Refraction
In PBR, we preserve the law of energy conservation by first finding Reflection part(Specular) and then Refraction part(Diffuse) which is "1.0 - (Reflection)", thereby conserving total energy.
Reflectance Equation
All the magic of having amazing visuals is this equation here.
Here, we solve this equation numerically by taking small steps in a hemisphere around a
Main terms of interest: L and BRDF term.
- Term L
-
This represents the Radiance at point "p" w.r.t. incoming direction vector "Wi"
- BRDF Term